Methods and systems for the continuous in-line coating and fabrication of hoop steel rebar for concrete structures

Abstract

Methods and systems are provided for the continuous coating and fabrication of spiraled steel rebar product for concrete structures. Specifically, methods and systems are provided by which linear uncoated rebar is supplied to a polymeric (preferably, epoxy) powder-coating unit whereby a substantially uniform coating layer of a polymeric material is applied onto the uncoated rebar to form a linear coated rebar; and thereafter the linear coated rebar is bent into a spiraled steel rebar product. The bending unit employed to bend the linear coated rebar includes a series of bending wheels having separated upstream and downstream bending wheels and a central bending wheel which is disposed between and below these upstream and downstream bending wheels. By bringing the linear coated rebar into contact with the series of bending wheels, the rebar may be bent gently into spiraled steel rebar product without damage to the polymeric surface coating. In this regard, it has been found that such gentle bending of the coated rebar may be advantageously accomplished using bending wheels which include a rubber-like tire mounted on a rigid rotatable wheel member.

1. A method of continuously coating and fabricating spiraled steel rebar product for concrete structures comprising the sequential steps of:
 (a) supplying a linear uncoated rebar to a polymeric powder-coating unit;  
 (b) applying a substantially uniform coating layer of a polymeric material onto the uncoated rebar to form a linear coated rebar; and thereafter  
 (c) bending the linear coated rebar into a spiraled steel rebar product, wherein between steps (a) and (b) there is practiced the step of,  
 (a1) abrading the surface of the linear uncoated rebar by directing a dry grit against the surface of the linear uncoated rebar with sufficient abrasive force to remove surface debris and/or oxidation therefrom and to provide a desired anchor profile to improve mechanical adherence of the coating layer of polymeric material.  
 
   
   
     2. The method of  claim 1 , wherein step (c) includes bending the linear coated rebar by bringing the linear coated rebar into contact with a series of bending wheels comprised of separated upstream and downstream bending wheels and a central bending wheel which is disposed between and below said upstream and downstream bending wheels. 
   
   
     3. The method of  claim 2 , wherein step (c) is practiced using bending wheels which include a rubber tire mounted on a rigid rotatable wheel member. 
   
   
     4. The method of  claim 3 , wherein step (a) includes the step of (a2) heating the uncoated rebar to an elevated temperature sufficient to fuse an epoxy powder, and wherein step (b) includes the step of (b1) electrostatically spray coating the heated and uncoated rebar with the epoxy powder and allowing the epoxy powder to fuse to thereby form a coated rebar having a substantially uniform coating of epoxy, and thereafter (b2) curing the epoxy coating on the coated rebar. 
   
   
     5. The method of  claim 4 , wherein after step (b2) and before step (c), there is practiced subjecting the coated rebar to a water quench. 
   
   
     6. The method of  claim 4 , wherein step (a2) is practiced by passing the uncoated rebar through an induction heater. 
   
   
     7. The method of  claim 6 , wherein the rebar is heated to a temperature of at least about 450° F. 
   
   
     8. The method of  claim 4 , wherein prior to step (a1), there is practiced the step of uncoiling the uncoated rebar from a supply coil thereof. 
   
   
     9. The method of  claim 8 , wherein step (a1) includes the step of (a3) straightening the uncoiled and uncoated rebar. 
   
   
     10. The method of  claim 1  or  4 , which further includes between steps (b) and (c) the step of determining defects in the epoxy coating. 
   
   
     11. A system for the continuous coating and fabrication of spiraled steel rebar product for concrete structures comprising:
 (a) a polymeric powder-coating unit which receives uncoated linear rebar and applies a substantially uniform coating layer of a polymeric material onto exterior surface of the uncoated rebar to form a linear coated rebar; and  
 (b) a bending unit for bending the linear coated rebar into a spiraled steel rebar product; and  
 (c) an abrading unit disposed upstream of the coating unit for directing a dry grit against a surface of the linear uncoated rebar with sufficient abrasive force to remove surface debris and/or oxidation therefrom and to provide a desired anchor profile to improve mechanical adherence of the coating layer of polymeric material.  
 
   
   
     12. The system of  claim 11 , wherein the bending unit includes a series of bending wheels which contact the linear coated rebar during bending, said series of bending wheels being comprised of separated upstream and downstream bending wheels and a central bending wheel which is disposed between and below said upstream and downstream bending wheels. 
   
   
     13. The system of  claim 12 , wherein the upstream, downstream and central bending wheels include a rubber tire mounted on a rigid rotatable wheel member. 
   
   
     14. The system of  claim 13 , which further comprises (a1) a heating unit for heating the uncoated rebar to an elevated temperature sufficient to fuse an epoxy powder, and (a2) a coating unit for electrostatically spray coating the heated and uncoated rebar with the epoxy powder and allowing the epoxy powder to fuse to thereby form a coated rebar having a substantially uniform coating of epoxy. 
   
   
     15. The system of  claim 14 , further comprising a quench cabinet downstream of said coating unit for spraying the coated rebar with a water quench. 
   
   
     16. The system of  claim 14 , wherein the heating unit includes an induction heater. 
   
   
     17. The system of  claim 16 , wherein the inducting heater is capable of heating the uncoated rebar to a temperature of at least about 450° F. 
   
   
     18. The system of  claim 14 , comprising a rebar straightener for straightening uncoated rebar which is uncoiled from a supply coil thereof. 
   
   
     19. The system of  claim 11  or  15 , which further includes a coating defect detection system for determining defects in the coating layer of polymeric material. 
   
   
     20. The system of  claim 11 , wherein the bending unit includes a support spool which is connected to and extends coaxially outwardly from the central bending wheel in a cantilevered manner. 
   
   
     21. A method of continuously coating and fabricating spiraled steel rebar product for concrete structures comprising the steps of:
 (a) providing a supply coil of uncoated rebar;  
 (b) uncoiling the uncoated rebar from the supply coil thereof and removing coil-shape memory from the uncoiled and uncoated rebar to provide linear uncoated rebar;  
 (c) supplying the linear uncoated rebar to a polymeric powder-coating unit and electrostatically spray-coating a substantially uniform coating layer of a polymeric coating material onto the uncoated rebar to form a linear coated rebar; and thereafter  
 (d) bending the linear coated rebar into a spiraled steel rebar product; wherein  
 (e) prior to electrostatically spray-coating the uncoated rebar, there is practiced the steps of (i) abrading the uncoated rebar surface to achieve a desired anchor profile for the polymeric coating material, and (ii) heating the uncoated rebar.  
 
   
   
     22. The method of  claim 21 , further comprising heating the uncoated rebar to an elevated temperature sufficient to fuse the polymeric powder. 
   
   
     23. The method of  claim 21 , wherein step (c) is practiced by electrostatically spray-coating the uncoated rebar with an epoxy. 
   
   
     24. The method of  claim 23 , comprising curing the epoxy coating on the coated rebar. 
   
   
     25. The method of  claim 24 , comprising after curing, subjecting the coated rebar to a water quench. 
   
   
     26. The method of  claim 24 , further comprising testing the coated rebar for coating defects. 
   
   
     27. The method of  claim 26 , wherein said step of testing the coated rebar comprises bringing the coated rebar into contact with wet sponge material charged with an electrical potential. 
   
   
     28. The method of  claim 27 , wherein said step of testing the coated rebar comprises generating an alarm in response to detection of a coating defect by the electrically charged wet sponge material. 
   
   
     29. A system for continuously coating and fabricating spiraled steel rebar product for concrete structures comprising:
 (a) a rebar straightener for uncoiling uncoated rebar from a supply coil thereof and removing coil-shape memory from the uncoiled and uncoated rebar to provide linear uncoated rebar;  
 (b) an abrading unit for abrading the surface of the uncoated linear rebar to achieve a desired anchor profile for a polymeric coating material;  
 (c) a polymeric powder-coating unit for applying a substantially uniform coating layer of a polymeric coating material onto the uncoated linear rebar to form a linear coated rebar; and  
 (d) a bending unit for bending the linear coated rebar into a spiraled steel rebar product.  
 
   
   
     30. The system of  claim 29 , further comprising a heating unit for heating the uncoated rebar to an elevated temperature sufficient to fuse a polymeric powder. 
   
   
     31. The system of  claim 29 , wherein said polymeric powder-coating unit comprises an electrostatic spray-coating nozzle. 
   
   
     32. The system of  claim 29 , comprising upstream of said powder-coating unit (i) the abrading unit and (ii) a heater for heating the uncoated rebar. 
   
   
     33. The system of  claim 29 , further comprising a curing unit for curing the polymeric coating material on the coated rebar. 
   
   
     34. The system of  claim 33 , wherein said curing unit comprises a quench cabinet for subjecting the coated rebar to a water quench. 
   
   
     35. The system of  claim 29 , further comprising a testing unit for testing the coated rebar for coating defects. 
   
   
     36. The system of  claim 35 , wherein testing unit comprises wet sponge material, and an electrical potential generator connected electrically to said wet sponge material for charging the wet sponge material with an electrical potential. 
   
   
     37. The system of  claim 36 , wherein said testing unit further comprises an alarm unit which generates an alarm in response to detection of a coating defect by the electrically charged wet sponge material. 
   
   
     38. The system of  claim 36 , wherein said testing unit further comprises an alarm unit which generates an alarm in response to detection of a coating defect by the electrically charged wet sponge material. 
   
   
     39. A method of continuously coating and fabricating spiraled steel rebar product for concrete structures comprising the steps of:
 (a) providing a supply coil of uncoated rebar;  
 (b) uncoiling the uncoated rebar from the supply coil thereof and removing coil-shape memory from the uncoiled and uncoated rebar to provide linear uncoated rebar;  
 (c) supplying the linear uncoated rebar to a polymeric powder-coating unit and applying a substantially uniform coating layer of a polymeric coating material onto the uncoated rebar to form a linear coated rebar;  
 (d) testing the linear coated rebar for coating defects by bringing the coated rebar into contact with wet sponge material charged with an electrical potential; and thereafter  
 (e) bending the linear coated rebar into a spiraled steel rebar product.  
 
   
   
     40. The method of  claim 39 , wherein step (d) comprises the step (d1) generating an alarm in response to detection of a coating defect by the electrically charged wet sponge material. 
   
   
     41. A system for continuously coating and fabricating spiraled steel rebar product for concrete structures comprising:
 (a) a rebar straightener for uncoiling uncoated rebar from a supply coil thereof and removing coil-shape memory from the uncoiled and uncoated rebar to provide linear uncoated rebar;  
 (b) a polymeric powder-coating unit for applying a substantially uniform coating layer of a polymeric coating material onto the uncoated linear rebar to form a linear coated rebar;  
 (c) a testing unit for testing the coated rebar for coating defects, wherein said testing unit comprises wet sponge material, and an electrical potential generator connected electrically to said wet sponge material for charging the wet sponge material with an electrical potential; and  
 (d) a bending unit for bending the linear coated rebar into a spiraled steel rebar product.